Field of the Invention
The present invention relates to the field of sensors for vehicle tyres, and particularly to a tyre sensor device.
Overview of the Related Art
The incorporation of electronic devices within pneumatic tyres is taking a greater importance in order to increase the safety of vehicles. Tyre electronics may include sensors and other components suitable for obtaining information regarding the behavior of a tyre, as well as various physical parameters thereof, such as for example temperature, pressure, number of tyre revolutions, vehicle speed, etc.
Such information may become useful in tyre monitoring and/or alarm systems.
Furthermore, active control/safety systems of the vehicle may be based on information sent from sensor devices provided in the tyres.
Active safety systems use information about the external environment of a vehicle to change the vehicle behavior in pre-crash time period or during the crash event, with the ultimate goal of avoiding a crash altogether. Initially, active safety systems were primarily focused on improving the vehicle longitudinal motion dynamics, in particular, on more effective braking Anti-lock Braking Systems (ABS) and Traction Control (TC) systems. TC systems prevent the wheel from slipping while improving vehicle stability and steerability by maximizing the tractive and lateral forces between the vehicle's tyre and the road. These systems were followed by more powerful vehicle stability control systems, e.g., Electronic Stability Program (ESP), Vehicle Stability Control (VSC), and Dynamic Stability Control (DSC). These latter systems use both brakes and engine torque to stabilize the vehicle in extreme handling situations by controlling the yaw motion. Active suspension systems are also an important part in vehicle active safety systems. They have been traditionally designed by trading-off three conflicting criteria: road holding, load carrying and passenger comfort. The suspension system has to support the vehicle, provide directional control during handling manoeuvres and provide effective isolation of passengers/payload from road disturbances.
The active safety control systems described above are based upon the estimation of vehicle dynamics variables such as forces, load transfer, tire-road friction. The more accurate and “real time” the parameter estimation, the better the overall performance of the control system. Currently, most of these variables are indirectly estimated using on-board sensors, and are not very accurate. Using measurements made by sensors fitted on the vehicle tyres would provide far more accurate estimation of the parameters relevant to the vehicle dynamics.